A sintered bearing is a porous body having innumerable inner pores, which are usually impregnated with a lubricating fluid (e.g., a lubricating oil) during use. Under such a condition, when the sintered bearing rotates relative to a shaft inserted inside the inner periphery of the sintered bearing, the lubricating oil retained in the inner pores of the sintered bearing seeps onto an inner peripheral surface (bearing surface) of the sintered bearing with a rise in temperature. The seeped lubricating oil forms an oil film in a bearing gap between the bearing surface of the sintered bearing and an outer peripheral surface of the shaft, and thus the shaft is relatively rotatably supported.
For example, Patent Document 1 listed below describes a copper-iron-based sintered bearing that is composed primarily of iron and copper, and which is produced by compacting and sintering a copper-coated iron powder, in which an iron powder is coated with copper in an amount of greater than or equal to 10 mass % and less than 30 mass %, and the granularity is less than or equal to 80 mesh.